Evacuated tube transport system

ABSTRACT

A capsule for an evacuated tube transport system, the capsule comprising a capsule body for carrying passengers within an evacuated tube; a first door disposed in a first end of the body; and a first coupling mechanism and a first sealing mechanism arranged respectively to couple the capsule to another capsule at the end of the body while the capsules are moving and to establish a seal around the door and a corresponding door in the other capsule to enable passengers to move from one capsule to another through the doors without exposing the passengers to the pressure of the evacuated tube.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of International ApplicationNo. PCT/AU2011/001604, filed Dec. 13, 2011, which claims priority fromAustralian Application No. 2010905504, filed Dec. 16, 2010, andAustralian Application No. 2011901931, filed May 18, 2011. The contentsof the prior applications are incorporated herein by reference in theirentirety.

FIELD

The present invention relates to an evacuated tube transport system aswell as a transport method.

BACKGROUND

Trains are the dominant form of ground-based mass-transport. A widevariety of such trains are deployed ranging from diesel and electricpowered trains to even more recent deployment of magnetic-levitationbased trains. Such trains require significant energy input in order tobe driven and, at the speeds they currently achieve, air resistancebecomes a significant factor.

One previously suggested alternative is to place a train or capsule inan evacuated tube. By placing the vehicle to be transported in anevacuated tube, the effective air resistance can be reduced allowing forfaster or more economical travel. While such systems have been proposed,to the applicant's knowledge, none have been implemented successfullyfor passenger travel.

Accordingly, there is a need for an alternative evacuated tube basedtransport system.

SUMMARY OF THE INVENTION

In a first aspect of the invention, there is provided a capsule for anevacuated tube transport system, the capsule comprising:

-   -   a cylindrical capsule body for carrying passengers within an        evacuated tube;    -   a first door disposed in a first end of the body; and    -   a first coupling mechanism and a first sealing mechanism        arranged respectively to couple the capsule to another capsule        at the end of the body while the capsules are moving and to        establish a seal around the door and a corresponding door in the        other capsule to enable passengers to move from one capsule to        another through the doors without exposing the passengers to the        pressure of the evacuated tube.

In an embodiment, the capsule comprises a second door in a second end ofthe body, a second coupling mechanism and a second sealing mechanismassociated with the another door whereby the capsule can be coupled toanother capsule at either end of the capsule.

In an embodiment, the capsule comprises a pump associated with at leastone of the first and second doors operable to equalise the air pressurein the region between two doors when coupled with the air pressure in acabin of the capsule.

In an embodiment, the capsule comprises at least one further door in aside of the capsule to enable passengers to enter or exit the capsulewhen the capsule is stopped.

In an embodiment, the capsule comprises a plurality of spaced apartfluid tanks disposed in a bottom portion of the capsule, the fluid tanksin fluid communication with one another so that fluid can be movedbetween tanks to alter weight distribution of the fluid.

In an embodiment, the fluid tanks contain baffles to restrict fluidmovement within the capsule.

In an embodiment, the capsule comprises a plurality of extendable wheelsarranged at radial spacing from one another to enable engagement betweenthe wheels and an interior of the evacuated tube.

In an embodiment, the capsule comprises a first reservoir arranged to bemaintained at a pressure higher than the evacuated tube, the firstreservoir in fluid communication with a plurality of vents disposed inan underside of the capsule to enable gas to be vented from the firstreservoir to form a gas cushion under the capsule.

In an embodiment, the capsule comprises at least one inlet via which gasis injected into the capsule to maintain the first reservoir at apressure higher than the evacuated tube.

In an embodiment, the capsule comprises a holding reservoir in fluidcommunication with the inlet and the first reservoir such that gasinjected into the capsule is held in the holding reservoir prior tobeing moved to the first reservoir.

In an embodiment, the capsule comprises at least one pressure controllednon-return valve between the holding reservoir and the first reservoir.

In an embodiment, the capsule comprises a cabin arranged to bemaintained at a first pressure suitable for carrying passengers and asecond reservoir disposed between the first reservoir and the cabinetand arranged to be maintained at a pressure lower than the firstpressure.

In a second aspect of the invention, there is provided an evacuated tubetransport system comprising:

-   -   a tube extending between an origin and a destination;    -   a capsule disposed within the tube, the capsule comprising at        least one indented region on an underside of the capsule;    -   a plurality of gas injectors disposed between the origin and the        destination for injecting gas into the evacuated tube as the        capsule passes the gas injector to apply the gas to the at least        one indented region to thereby apply motive force to the capsule        and maintain a cushion of gas underneath the capsule.

In an embodiment, the gas is compressed air.

In an embodiment, the at least one gas injector is angled relative tothe direction of travel to apply motive force in the direction oftravel.

In an embodiment, the evacuated tube transport system further comprisesat least one gas injector angled relative to the direction of travel ofthe capsule to apply braking to the capsule.

In an embodiment, the evacuated tube transport system comprises aplurality of spaced apart vacuum pumps for evacuating the tube.

In an embodiment, the evacuated tube transport system comprises at leastone launching mechanism comprising:

-   -   a plate member moveable into the tube; and    -   a launching gas injector arranged to inject gas into the tube        between the launching plate and a capsule disposed in the tube        proximate the plate to thereby launch the capsule.

In an embodiment, the evacuated tube transport system comprises acapsule inserting mechanism comprising two tube sections disposed nextto one another, a mechanism for moving each of the tube sections betweenan operative position in which the tube section is connected with theevacuated tube and an inoperative position in which the tube section isnot connected to the tube, and a sealing mechanism for maintaining thepressure of the evacuated tube during movement of the tube sections.

In a third aspect of the invention, there is provided an evacuated tubetransport system comprising:

-   -   a plurality of capsules, each capsule comprising a cylindrical        capsule body for carrying passengers within the evacuated tube,        first and second doors disposed respectively in first and second        ends of the body, first and second coupling mechanisms and first        and second sealing mechanisms disposed respectively in first and        second ends of the body;    -   an origin launching mechanism arranged to launch at least one        originating capsule of the plurality capsules from an origin        such that it travels towards a destination;    -   an intermediate launching mechanism located at a first        intermediate position intermediate the origin and the        destination, the intermediate launching mechanism arranged to        launch at least one injected capsule of the plurality of        capsules in advance of the travelling originating capsule        whereafter the coupling and sealing mechanisms of the respective        doors form a connection between a rearwards most door of the        injected capsule and a forwards most door of the originating        capsule whereby passengers may move through the coupled capsules        such that passengers intending to disembark at a second        intermediate position may move to a rearwards most capsule        without being exposed to the pressure of the evacuated tube and        the rearwards most capsule may be decoupled to allow the        rearwards most capsule to be brought to a halt at the second        intermediate position.

In a fourth aspect of the invention, there is provided a transportmethod comprising:

-   -   launching one of a plurality of capsules from an origin with an        origin launching mechanism such that it travels towards a        destination, each capsule comprising a cylindrical capsule body        for carrying passengers within the evacuated tube, first and        second doors disposed respectively in first and second ends of        the body, first and second coupling mechanisms and first and        second sealing mechanisms disposed respectively in first and        second ends of the body;    -   launching at least one injected capsule of the plurality of        capsules in advance of the travelling originating capsule with        an intermediate launching mechanism located at a first        intermediate position intermediate the origin and the        destination;    -   forming a connection between a rearwards most door of the        injected capsule and a forwards most door of the originating        capsule with the coupling and sealing mechanisms of the        respective doors whereby passengers may move through the coupled        capsules such that passengers intending to disembark at a second        intermediate position may move to a rearwards most capsule        without being exposed to the pressure of the evacuated tube;    -   decoupling the rearwards most capsule to allow the rearwards        most capsule to be brought to a halt at the second intermediate        position such that the passengers can disembark.

In a fifth aspect of the present invention, there is provided a gascompression/vacuum system for providing compressed gas and creating avacuum for the operation of an evacuated tube transport system, the gascompression/vacuum system comprising:

-   -   a support structure for supporting part of the tube transport        system, the support structure having at least a first member and        a second member;    -   a first piston housed in the first member which is operable to        move within the first member to compress gas or create a vacuum        in the first member; and    -   a second piston housed in the second member which is operable to        move within the second member to compress gas or create a vacuum        in the second member.

In an embodiment, the first and second pistons are connected to eachother whereby movement of one of the pistons causes movement of theother piston in the opposite direction.

In an embodiment, the support structure comprises at least one tank forholding liquid, the liquid for use in causing movement of the pistons.

Other aspects, features and advantages of the invention will be apparentfrom the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring to the Figures there is shown an evacuated tube transportsystem in accordance with embodiments of the invention. In the drawings:

FIG. 1 is a schematic plan of an evacuated transport system of anembodiment of the invention;

FIGS. 2A, 2B and 2C illustrate a manner in which an evacuated tube maybe suspended above a landscape;

FIG. 3 is a schematic cross-sectional diagram of the capsule of anembodiment;

FIG. 4 is a schematic plan view of a capsule of an embodiment;

FIG. 5 is a detail a mechanism for compressed air delivery of anembodiment;

FIGS. 6A and 6B show detail of a set of adjustable air inlets;

FIG. 7 is a schematic plan of an alternative capsule docking station;

FIG. 8 is schematic of a system for providing compressed gas andcreating the vacuum required for the evacuated tube transport system;and

FIG. 9 is a schematic of a piston of the gas compression/vacuum systemof FIG. 8.

DETAILED DESCRIPTION

The drawings show an evacuated tube transport system 100 and a capsule130 for the evacuated tube transport system 100. The evacuated transportsystem is capable of moving passengers and freight from an originstation 101 to a destination station 104. Embodiments of the inventionallow capsules to be picked up and dropped off at intermediate stations102, 103 while at least one capsule continues to move. As will bedescribed in further detail below, the capsules 130 are moved within theevacuated tube 120 by the application of compressed air both at theorigin and at spaced apart locations along the evacuated tube 120. Theinjected air is removed by spaced apart vacuum pumps in order tomaintain the evacuated pressure of the tube. Compressed air is injectedto the underside of the capsules both to apply motive force and toassist in the establishment of a cushion of compressed air underneaththe capsule such that the system takes advantage of the so-calledhovercraft effect.

Referring to FIG. 1 there is shown a schematic plan view of an evacuatedtube transport system 100 in accordance with an embodiment of theinvention.

In FIG. 1, the capsules 130 are represented by circles, although inpractice the capsules are cylindrical so as to act in effect as a pistontravelling within a cylinder formed by the evacuated tube 120. In FIG. 1two capsules 130A, 130B are located at an origin station 101. In orderto launch the capsules 130A, 130B, compressed air is injected into theevacuated tube between the rearward most capsule 130A and an end 121 ofthe evacuated tube. The compressed air applies a motive force to therear of the capsule 130A. This force is transferred through a couplingto the forward most capsule 103B. Accordingly, the injection ofcompressed air causes the capsule to begin travelling towards thedestination station 104.

The system 100 is operated in order to allow additional capsules to beinserted into the tube at the intermediate positions of intermediatestations 102, 103 and for capsules to be dropped off at these stations102, 103 without the other capsules coming to a rest. To this end, asshown in FIG. 4, each capsule 130 has a first door 420A and a seconddoor 420B which enables a passenger to enter and exit the capsule intoanother capsule when the capsules are appropriately joined together aswill be described in further detail below.

As the capsules 130A, 130B approach the intermediate destination 102, athird capsule 130C is moved into the tube by means of capsuleinsertion/extraction mechanism 150A. Each capsule insertion/extractionmechanism comprises a pair of tube sections of the approximate length ofthe number of capsules that they are intended to insert. FIG. 1 showstwo dual capsule insertion mechanisms 140A,140B and two singular capsuleinsertion mechanism 150A,150B. The insertion/extraction mechanism 150Ahas a launching mechanism which includes a metal plate 151A which isslid into the tube while maintaining the vacuum such that compressed aircan be inserted into the tube between the metal plate 151A and capsule130C to cause the capsule to begin to move. Accordingly the capsule 130Cis accelerated in advance of capsule 130B such that the pace of thecapsule 130C matches the pace of capsule 130B when capsule 130B catchesup to capsule 130C. Capsule 130A will be dropped off at intermediatestation 102. Accordingly, all passengers who wish to disembark at firstintermediate station 102 ensure is that they are in capsule 130A by thetime it is to be decoupled from capsule 130B. According to theembodiment, passengers who wish to, can disembark at second intermediatestation 103 irrespective of whether they got on at the firstintermediate station 102. In this respect, it will be appreciated thatonce capsule 130A has been decoupled and capsule 130B has caught up tocapsule 130C, there will be a train comprised of capsules 130B and 130Ctravelling towards the second station 103. Passengers wishing todisembark at station 103 who are in capsule 130C move through the doors420 of capsules 130C and 130B into capsule 130B. Any passengers notwishing to disembark at the second intermediate station move intocapsule 130C. As the capsules approach the second intermediatedestination, capsule 130D will be moved from the retracted positionshown in FIG. 1 to an inserted position and accelerated in advance ofcapsules 130B, 130C. Capsule 130B will be decoupled and brought to astop at the second intermediate station allowing passengers todisembark. Capsule 130C will join capsule 130D and proceed towards thedestination station 104 where both capsules 130C, 130D will be broughtto a stop.

As shown in FIG. 1 two further capsules 130E and 130F can be held in theextracted position in the capsule extraction/injection mechanism 140B atthe destination until capsules 130C and 130D arrive. At this point, thecapsules 130E, 130F can be inserted into the system while capsules 130C,130D are moved to an extracted position outside of the evacuated tubeand passengers can disembark. While in this example, a single tube isdescribed, in other embodiments, there may be pairs of tubes one for theoutward journey and another for the return journey. In such anembodiment, capsules 130C, 130D are moved to an extracted position wherepassengers disembark. Other passengers then board capsules 130C and 130Dbefore the capsules are inserted into the return tube.

While the preferred embodiment shows capsules being moved into and outof the evacuated tube by insertion/extraction mechanisms 140,150 personsskilled in the art will appreciate that in some other embodiments itwill not be necessary to remove the to capsules from the tube. Forexample, a capsule at the destination can be left in the tube until itis desired to launch it again and passengers can be disembarked througha side door in the capsule by sealing that to an appropriate port in awall in the evacuated tube. An example of such a side door 311 is shownin the cabin 310 of the capsule 130 in FIG. 3. In one advantageousembodiment, capsules 130 are propelled in a fixed sequence within thetube such that it is not necessary to add or remove capsules from thetube and compressed air is applied solely to the underside and rear ofthe capsule. Further, in embodiments where insertion/extractionmechanisms 140,150 are used, the mechanism need not always be used, forexample an express capsule can pass an intermediate station.

FIG. 2 illustrates that in the preferred embodiment the evacuated tube120 is advantageously supported by a series of suspension bridges. Thisallows the tube 120 to be supported above the ground 260. FIG. 2A showsone section 200 of suspension bridge having main suspension cables 210and stabilising cables 230 which hold the evacuated tube 120 betweenadjacent towers 250A, 250B. Lateral cables 220 provide additionalstabilisation and bracing.

FIG. 2B is a view along a section identified by lines A-A in FIG. 2A andshows that in embodiments of the invention there may be more than oneevacuated tube, specifically FIG. 2B shows four such tubes. FIG. 2C is aplan view showing the arrangement of the stabilising cables 230.

One advantage of the system is that it is not necessary to disrupt theexisting landscape 260 as the evacuated tube can be held at a positionabove the landscape such that the landscape is still usable. This canreduce the cost of installation as the entirety of the underlying landdoes not need to be purchased outright. Further, as there will not bemany capsules in a length of evacuated tube at any time, relatively longspans can be achieved between neighbouring towers 250A, 250B.

FIG. 3 shows schematically the manner in which the evacuated transportsystem operates. Along the length of the evacuated tube 120 areperiodically placed compressed air injectors 350 and vacuum pumps 360.The compressed air injectors are used to inject air to the under surfaceof the capsule and against the end of the capsule. The injectors areangled relative to the path of travel either to apply force in thedirection of travel or force against the direction of travel in order tobrake the capsule. The capsule 130 contains an air reservoir in the formof a pressure chamber 330 (or a plurality of air reservoirs) under thefloor 320 of cabin 310. Compressed air finds its way into the reservoirvia an inlet 520 and then is vented outwardly to form an air cushion 340underneath the capsule 130. The pressure chamber 330 can also be used tosupply fresh air to the cabin 310.

The air inlet and vents are shown in more detail in FIG. 5. The capsulehas two cavities 530, 540 which extend around the circumference of thecapsule. The first cavity 540 is evacuated to provide for sound andthermal insulation. The first cavity can be used as a source of vacuum,for example to remove stale air from the cabin or to assist in dockingas described below. The second cavity 530 is filled with compressed airin order to produce the hovercraft effect 340 described previously.Specifically, air injector 350 injects air through a valve 510 in thefloor of the evacuated tube 120. The air is admitted into the airreservoir 330 via inlet 520 which incorporates a one way pressure valve560. The air is injected at a higher pressure than the pressure in thesecond annular cavity 530 and accordingly can be controlled to flow viapressure valves 552 through venting outlets 551 and ultimately outthrough vents 531 in the base of the capsule to deliver jets of airwhich provide the hovercraft effect. Longitudinal members 570A,570B helpconfine the air in the desired area to aid the hovercraft effect.

One example of an inlet structure is shown in FIGS. 6A and 6B from whichwill be appreciated that a plurality of inlets are provided in the baseof the capsule. The inlets take the form of a plurality of blades 620such that motive force can be applied and the air then finds its wayinto the reservoir as described above. The blades are mounted forpivotal movement so that there angles can be adjusted (and hence the airinlets can be adjusted). This allows adjustment of both drive and airintake.

In one embodiment, a plurality of automatic pressure sensitive valvesdisposed along the length of the evacuated tube can be used to bring thesystem to a halt by opening the tube to atmospheric pressure in anemergency.

Referring to FIG. 4, further features of the invention are shown. Asdescribed above, the capsules can be coupled while they are moving. Tothis end, the capsule includes a plurality of magnetic couplers 430. Thecouplers which are diagonally opposed to one another have the samepolarity whereas the couplers on each end have different polarities.Thus, couplers 430A and 430D have one polarity and couplers 430B and430C have the other polarity such that they will magnetically couple.One door acts as a socket while the other door is a spigot such that onedoor is received inside the other and seals (e.g. o-rings), seal thedoors. Pumps 421 are co-located with the doors 420 to align the pressurein the area trapped between the doors with the cabin in a manneradvantageous to operation of an air lock.

In another embodiment, coupling can be achieved using flat hingedgrappling hooks or other suitable coupling. In some embodiments theonboard sources of pressure and vacuum can be used to cushion thedocking process and increase the strength of the coupling respectively.

Ceramic rings at each end of the capsule act as piston rings which canadmit cold compressed air from the capsule to maintain separation of thecapsule from the tube or in the event of a system failure.

The capsule has electrically driven wheels disposed, for example at eachend at different radiuses. In one example, they are disposed relative tothe 12 midday orientation of the capsule at 60,180 and 300 degrees andare arranged to engage the tube as necessary, for example when dockingat a station or in the case of power failure.

The capsule has an electricity supply supplied by a plurality ofreplaceable or rechargeable battery packs. In one embodiment, acompressed air turbine generator is disposed in an inlet to recharge thebatteries. The electricity supply can be used to power lights, heating,cooling etc. In some embodiments, the air in the cabin is sufficient forthe journey between each station where it can be re-supplied. In otherembodiments, it may be resupplied from the injected air. Similarly,water and sewerage can be added and removed from the capsules when theyare docked.

Any fire in the cabin can then be extinguished by evacuated cavity 540by means of valves connecting it to the cabin which will reduce therelative portion of the oxygen in the air.

The capsule has an electricity supply supplied by a plurality ofreplaceable battery packs. The air in the cabin can be supplied from airon board the capsule, for example from the air cylinder. Similarly,water and sewerage can be added and removed from the capsules when theyare docked and undocked.

As described above, in order to insert capsules into the tube areplacement tube can be moved laterally on rails placing the second tubein-line with the evacuated tube. A pair of steel plates are contained atthe end of each tube and are slideably movable in either direction andare sealed with a pressurised gasket. When it is desired to launch thecapsule the front steel plate is removed while the rear steel plate isleft in place. The two joints in the main tube are sealed by two slidingouter tubes with gaskets.

Persons skilled in the art will appreciate that the lateral movement ofa single pair of tubes is not the only manner in which additional tubescan be brought in line. For example, a rotating barrel of tubes can beused to bring the tubes in line. Persons skilled in the art willappreciate that other mechanism can be used to exchange capsules duringloading and unloading. FIG. 7 shows an example of an alternative dockingstation. Capsules arriving via tubes 120A,120B are received in dockingareas 710A,710B of turntable 705 mounted within support structure 720from which passengers can access the capsules. Other docking areas arelocated around the perimeter of the turntable 705. Thus, for example,docking areas 711A,711B can be brought into alignment with tubes120B,120A by rotating the turntable. The turntable is in the form of a30 m diameter cylinder which is displaceable along its vertical axis (aswell as being rotatable. This allows, a plurality of tubes 120 to bemounted at different heights relative to the docking station and forcapsule to be moved between tubes 120 at different heights.

FIG. 8 shows another embodiment of the invention in which the towers 250of the suspension bridges shown in FIG. 2 can be used in providingcompressed gas and creating the vacuum required for the tube transportsystem 100. Typically, the gas is air, but in other embodiments othersuitable gases may be employed. The tower 250 shown in FIG. 8 and inparticular the tower's columns 801, 802 and at least some of thecross-members are constructed from hollow members in the form of steeltubes. A gas compression/vacuum system 810 is provided within the hollowmembers of the tower 250. The compression/vacuum system 810 comprisesupper and lower tanks 811, 812 for holding liquid. Typically this liquidis water but in other embodiments other liquids such as oil might beused. At least part of the upper tank 811 comprises upper portions ofthe tower's columns 801, 802 and at least part of the lower tankcomprises lower portions of the tower's columns. The upper tank 811 hasfirst and second valves 813, 814 which open to the respective columns801, 802 and the lower tank 812 has third and fourth valves 815, 816which open to the respective columns.

The compression/vacuum system 810 also comprises a release conduit 817for releasing liquid that has entered the first or second columns 801,802 of the tower during operation of the compression/vacuum system 810into the lower tank 812. Although it is to be appreciated that therelease conduit 817 could be configured to release liquid to the uppertank 811 or to both tanks. The release conduit 817 in the embodimentshown in FIG. 8 comprises a hollow member extending between the towercolumns 801, 802. The release conduit 817 is located above and spacedfrom the lower tank 812 and has release valves 818, 819 located atrespective first and second ends of the conduit.

The gas compression/vacuum system 810 also comprises first and secondpistons 820, 821 respectively located in the tower's columns 801, 802between the upper and lower tanks 811, 812. The pistons 820, 821 areconnected to each other by means of a cable 822 supported on appropriatepulleys 823. The pistons 820, 821 are able to move vertically withintheir respective columns. FIG. 9 shows one of the pistons in greaterdetail. Each piston is provided with sealing rings 826 to form a sealwith the inner surface of its respective column. A piston valve 825 isprovided on each piston to enable fluid to flow through the piston,which may be particularly useful during maintenance of thecompression/vacuum system and resetting the system mid-cycle.

FIG. 8 shows an initial condition for the gas compression/vacuum system810, which operates cyclically. In this initial condition, the uppertank 811 holds a substantially greater volume of liquid than the lowertank 812 and first to fourth valves 813-816 are closed. One piston 820,in this initial condition, is located in an upper portion of its column801 and the other piston 820 is located in a lower portion of its column802. The piston valves 825 of each piston 820, 821 and the releasevalves 818, 819 of the release conduit 817 are also closed.

Operation of the gas compression/vacuum system 810 begins by opening thefirst valve 813 (keeping the second-fourth valves 814-816, the releasevalves 818, 819 and the piston valves 825 closed). As a result liquidflows from the upper tank 811 into the column 801 pushing the firstpiston 820 down and compressing the gas beneath the piston 820. At thesame time, the downward movement of the first piston 820 causes thesecond piston 821 to be drawn upwards in the second column 802, reducingthe gas pressure (i.e. creating a “vacuum”) below the second piston 821.

As shown in FIG. 8, the transport system 100 is connected to both of thecolumns 801, 802. The transport system 100 is provided with suitablevalve assembly 850 to draw off compressed gas and utilise the vacuumcreated by the gas compression/vacuum system 810 within the columns 801,802 as required.

Once the first piston 820 has reached its maximum lower position in thefirst column 801 and the compressed gas and vacuum have beensubstantially used by the transport system 100, the gascompression/vacuum system 810 is ‘reset’ in order for system 810 tobegin another process of compressing gas and creating a vacuum but inopposite columns of the tower 250 this time. It is noted that themaximum lower position of the piston is below the release conduit 817.The ‘resetting’ of the system 810 involves closing the first valve 813of the upper tank 811 followed by opening the both release valves 818,819 as well as the fourth valve 816 of the lower tank 812. This enablesthe liquid that has flowed into the first column 801 from the upper tank811 to be released from the first column into the lower tank via therelease conduit 817. Once all the water has been delivered from thefirst column 801 to the lower tank 812 the valves 816, 818, 819 areclosed. The system 810 is also reset by operating appropriate valving toallow gas into the second column 802 thereby resetting its internal gaspressure to atmospheric.

The gas compression/vacuum system 810 is then ready for the next stageof the cycle in which second valve 814 of the upper tank 811 is opened(whilst keeping first, third and fourth valves 813, 815, 816, therelease valves 817, 818 and the piston valves 825 closed). This enablesliquid to flow from the upper tank 811 into the second column 802pushing the second piston 821 down and compressing the gas beneath thepiston 821. At the same time, the downward movement of the second piston821 causes the second piston 821 to be drawn upwards in the first column801, reducing the gas pressure (i.e. creating a “vacuum”) below thefirst piston 820. At the end of this step in the cycle, liquid isreleased from the second column 802 by opening the release valves 818,819 and the third valve 815 of the lower tank 811 so that liquid flowsfrom the second column 802 and into the lower tank 811 via the releaseconduit 817. The system 810 is once again reset.

It is noted that the transport system 100 is arranged so that itscompressed gas and vacuum lines can draw off compressed gas and utilisethe vacuum created in either of the columns 801, 802 as determined bywhich phase of the operating cycle the gas compression/vacuum system 810is in.

The gas compression/vacuum system 810 also comprises a pump 830 forreturning liquid from the lower tank 812 to the upper tank 811 tofacilitate continual operation of the system 810. The pump 830 may bepowered by any suitable means, but preferably is powered by solarpanels, wind turbines or any other source of renewable energy. The pump830 typically operates semi-continuously for example if it is powered bysolar panels.

The gas compression/vacuum system 810 is configured so that there isalways sufficient liquid in the upper tank 811 to enable operation ofthe gas compression and vacuum creation cycle. Because the pump 830 mayonly operate semi-continuously, for example only during daylight hours,this requires:

-   -   Providing sufficient liquid in the system so that when the pump        830 can operate there is liquid in the lower tank 812 for it to        pump and so that there is always sufficient liquid in the upper        tank 811 for the pistons 820, 821 to operate to compress gas and        create a vacuum in the columns 801, 802;    -   Designing the tanks 811, 812 to be of sufficient volume to hold        the liquid required for the system 810    -   Configuring timing for the operation of the pump 830 with the        operation of the gas compression and vacuum creation cycle to        ensure that the pump 830 is operating whilst there liquid in the        lower tank 812.

Persons skilled in the art will appreciate that the transport system 100can also be used for freight with the capsules being removed at relevantpositions. In one embodiment, some tubes are used for freight and othersfor passengers. For example, referring to FIG. 2B, two tubes may be usedfor passengers and two for freight. In other embodiments freight, forexample premium freight, may be carried in passenger capsule byattendants moving the freight from capsule to capsule (e.g. usingtrollies) to ensure it is deposited at the is correct location.

Persons skilled in the art will appreciate that the transport system canrun effectively with compressed air with air compressors being used tofeed the air injectors 350. However, the injected gas could be of adifferent mix to air. For example, the oxygen content could be reducedto reduce the risk of fire.

Persons skilled in the art will appreciate that the invention has anumber of advantages. In particular because of the low air pressure inthe evacuated tube, the capsules can run at significant speeds withouteffective air resistance. The speed will vary from embodiment toembodiment and will depend on the distance between stations as thereneeds to be sufficient time to accelerate the capsules up to near thecruising speed so that capsules can be docked while moving.

Persons skilled in the art will appreciate that the tube protects thecapsules from an external weather. The tube can be formed of anysuitable material such as steel or carbon fibre. In some embodiments,plastic or plastic composite materials may be appropriate for the tube.Longitudinal holes could be provided within the wall of the tube toreduce the required volume of material to make the tubes. As compressedair is used to power the system, no dangerous or explosive materials areinvolved in powering the vehicle.

Persons skilled in the art will appreciate that the evacuated tubescould be disposed, where possible above existing railway lines so as tosupplement existing railway systems. The capsules are designed to carryapproximately 80 passengers, the tube itself is approximately 3 metersin diameter. The space in-between the cavities 540,530 is approximately150 mm.

Persons skilled in the art will appreciate that in other embodimentsfuel cells may be used or external combustion used to provide thecompressed air, for example using a hydrogen pipe beneath the main tube.In other embodiments, the air compressors can be powered by electricity.

It will be understood to persons skilled in the art of the inventionthat many modifications may be made without departing from the spiritand scope of the invention, in particular it will be apparent thatcertain features of embodiments of the invention can be employed to formfurther embodiments.

It is to be understood that, if any prior art is referred to herein,such reference does not constitute an admission that the prior art formsa part of the common general knowledge in the art in any country.

In the claims which follow and in the preceding description of theinvention, except where the context requires otherwise due to expresslanguage or necessary implication, the word “comprise” or variationssuch as “comprises” or “comprising” is used in an inclusive sense, i.e.to specify the presence of the stated features but not to preclude thepresence or addition of further features in various embodiments of theinvention.

The invention claimed is:
 1. A capsule for an evacuated tube transportsystem, the capsule comprising: a capsule body for carrying passengerswithin an evacuated tube; a first door disposed in a first end of thebody; a first coupling mechanism and a first sealing mechanism arrangedrespectively to couple the capsule to another capsule at the end of thebody while the capsules are moving and to establish a seal around thefirst door and a corresponding door in the other capsule to enablepassengers to move from one capsule to another through the doors withoutexposing the passengers to the pressure of the evacuated tube; and afirst reservoir arranged to be maintained at a pressure higher than theevacuated tube, the first reservoir in fluid communication with aplurality of vents disposed in an underside of the capsule to enable gasto be vented from the first reservoir to form a gas cushion under thecapsule.
 2. A capsule as claimed in claim 1, comprising a second door ina second end of the body, a second coupling mechanism and a secondsealing mechanism associated with the another door whereby the capsulecan be coupled to another capsule at either end of the capsule.
 3. Acapsule as claimed in claim 2, comprising a pump associated with atleast one of the first and second doors operable to equalize the airpressure in the region between two doors when coupled with the airpressure in a cabin of the capsule.
 4. A capsule as claimed in claim 1,comprising at least one further door in a side of the capsule to enablepassengers to enter or exit the capsule when the capsule is stopped. 5.A capsule as claimed in claim 1, comprising a plurality of spaced apartfluid tanks disposed in a bottom portion of the capsule, the fluid tanksin fluid communication with one another so that fluid can be movedbetween tanks to alter weight distribution of the fluid.
 6. A capsule asclaimed in claim 1, comprising a plurality of extendable wheels arrangedat radial spacing from one another to enable engagement between thewheels and an interior of the evacuated tube.
 7. A capsule as claimed inclaim 1, comprising at least one inlet via which gas is injected intothe capsule to maintain the first reservoir at a pressure higher thanthe evacuated tube.
 8. A capsule as claimed in claim 7, comprising aholding reservoir in fluid communication with the inlet and the firstreservoir such that gas injected into the capsule is held in the holdingreservoir prior to being moved to the first reservoir.
 9. A capsule asclaimed in claim 8, comprising at least one pressure controllednon-return valve between the holding reservoir and the first reservoir.10. A capsule as claimed in claim 1, comprising a cabin arranged to bemaintained at a first pressure suitable for carrying passengers and asecond reservoir disposed between the first reservoir and the cabin andarranged to be maintained at a pressure lower than the first pressure.